"Beeswarm chart" is the search term that will get you more examples.

Another great example http://www.nytimes.com/interactive/2013/05/25/sunday-review/...

I believe the webapp retrieves your message history from the phone in real time, and Whatsapp does not store messages on their servers once they have been delivered.

No. If you take the example animation, you can set border-left-color and border-right-color to transparent, and set border-top-width to 0. This will place the triangle in a bounding box of the correct width and height.

Google has a price protection program in place if you purchased after August 12. You have 15 days to claim at https://support.google.com/googleplay/contact/nexus_price

Message previews in the notification bar can be disabled.